Heretofore, there has been known a gap adjusting mechanism usable in a single facer to adjust a gap between a press or glue roll and a corrugating roll. For example, a gap adjusting mechanism for a single facer described in JP 58-042025 B (Patent Document 1) comprises: a pair of wedges each having a respective one of two oppositely-tapered surfaces engageable with each other; a gap adjustment shaft to which one of the wedges is fixed; and a motor for moving the gap adjustment shaft in its axial direction to change an engagement position between the oppositely-tapered surfaces of the wedges. The other wedge is fixed to a side plate of a pressure arm supporting a press roll. The press roll is rotatably supported in an eccentric hole of a circular bearing metal of the pressure arm. An air cylinder is coupled to the side plate of the pressure arm, in such a manner as to allow the other wedge to come into engagement with the one wedge, when it is activated.
The motor for moving the gap adjustment shaft in the axial direction is controlled by a comparison between a signal indicative of a thickness of a paperboard for a corrugated medium and a thickness of a paperboard for a linerboard, and a gap detection signal indicative of a gap between the press roll and a corrugating roll. According to the motor control, the gap adjustment shaft is moved in the axial direction to change the engagement position between the wedges, so that the gap between the press roll and the corrugating roll can be adjusted. In this specification, a thickness of a paperboard for a corrugated medium and a thickness of a paperboard for a linerboard will be simply described, respectively, as “a thickness of a corrugated medium” and “a thickness of a linerboard”.